Reformists in Iran are under pressure, detainees face torture and abuse, and people are being executed at an "alarming" rate, a UN monitor studying human rights in the tightly controlled country says.

The bleak picture presented to the UN Human Rights Council on March 13 comes ahead of a May 19 presidential election in Iran.

"All reports indicate a high level of control over citizens and that democratic space is severely limited," Asma Jahangir, the UN special rapporteur for Iran, told the council in Geneva.

Jahangir did not refer directly to the election, but she noted that three opposition figures who publicly challenged the official results of Iran's 2009 presidential election -- former Prime Minister Mir Hossein Musavi; his wife, university professor Zahra Rahnavard; and reformist cleric Mehdi Karrubi -- have been kept under house arrest for nearly six years without being formally charged.

Jahangir also voiced concern about state pressure on media workers and censorship efforts by the Iranian establishment.

As of December 13, 2016, "at least 24 journalists, bloggers, and social media activists were reportedly either in detention or sentenced for their peaceful activities,” she said in a written report on human rights violations in Iran, which was released on March 6.

Jahangir said she has received reports indicating that Iran continues to place restrictions on access to information by blocking websites, intimidating and prosecuting Internet users, bloggers and social media activists, and throttling Internet speeds.

In the March 6 report, Jahangir expressed deep concern over “the alarming level of executions” in Iran, where she said that at least 530 people were executed last year and 156 have been put to death this year.

At least five of those executed in 2016 were below the age of 18 at the time of their alleged offense, she said, noting that Iran has reportedly executed the highest number of juvenile offenders in the world during the past decade.

Jahangir urged the Iranian establishment to "immediately and unconditionally prohibit the sentencing of children to death and to engage in a comprehensive process of commutation of all death sentences handed down on persons currently on death row for crimes committed under the age of 18."

She also reiterated calls made by her predecessor to establish a moratorium on the use of the death penalty.

Iran has one of the highest execution rates in the world. Most people who are executed have been convicted of drug-related crimes.

Jahangir said that since her appointment last year, she has received “numerous reports about the use of torture and other cruel, inhuman, or degrading treatment or punishment," including the continued use of amputations, blinding, and flogging, as well as the use of prolonged period in solitary confinement for detainees.

She cited reports by Iranian media about a blinding sentence that was carried out in November in a prison near the capital, Tehran, and finger amputation sentences that were carried out in December for two men detained in Orumieh prison in northwest Iran.

Jahangir also highlighted child marriages in Iran where, according to the Tehran-based Association to Protect the Rights of Children, approximately 17 percent of all marriages involve girls married with old men.

She called on Iran to prohibit all forms of child marriage and raise awareness about the "harmful practice."

Jahangir also said that the situation of Iran’s recognized and unrecognized minorities remain of "serious concern."

"Bahai’s continue to be systematically discriminated, targeted, and deprived of the right to a livelihood,” Jahangiri said in her March 6 report.

The Baha'i faith is not recognized in the constitution of Iran, which has been ruled by a conservative Muslim establishment since the 1979 Islamic Revolution.

Jahangir said that 90 Baha’i believers are currently detained in Iran’s prison detained solely because of their religious beliefs and practices.

Jahangir also expressed concern over the state targeting of Iranian Christian converts and members of Sufi groups.

"These groups continue to face arbitrary arrest, harassment, and detention and are often accused of national security crimes such as 'acting against the national security' or 'propaganda against the state.'"